1. Field of the Invention
The present invention relates to a method for the patterned, selective metallization of a surface of a substrate.
2. Discussion of Related Art
German patent DE 100 15 213 relates to a process for metalizing at least one insulating layer of a component, in which likewise a plurality of planes are uncovered for metallization by patterning and forming connections between a plurality of insulating layers. Moreover, German patent DE 100 15 214 relates to a process for metalizing an insulator and/or a dielectric in which first of all the insulator is activated, then it is coated with a further insulator and the latter insulator is patterned, after which the first insulator is seeded and finally metallized.
Solution baths for electroless metallization preferably in aqueous solution are known, but they do have drawbacks. Firstly, the substrate has to be activated, i.e. partially etched, before a seeding layer, e.g. comprising palladium, can be applied, then allowing electroless deposition of a metallization. A separate process step is required to enable the seed layer to be patterned. Furthermore, the deposition rate drops as the layer thickness of the metallization increases, which means that the layer thicknesses which can be achieved are limited for economic reasons (time consumption). In addition, the chemistry of the baths is highly complex and requires constant, complex analysis to ensure that the processes in the solution baths are taking place as intended. Alternatively, the solution baths can be frequently changed or replaced, in which case environmental problems arise on account of the heavy metal content of the solutions. Moreover, four solutions are typically required, which entails a high level of outlay. The four baths can be divided into an etching bath, a seeding bath, a reduction bath and a final metallization bath. Finally, when changing a bath, to prevent the solutions from contaminating one another, the device which has been treated in the bath has to be rinsed, and this also reduces efficiency.
An article by J. M. Blackburn, D. P. Long, A. Cabanas, J. J. Watkins, Science 294 (2001) 141 relates to a process in which metal films which cover the entire surface can be generated from organometal precursors (for copper: bishexafluoroacetylacetonate-copper (II) and tetramethylheptanedionate-copper (II); for nickel: biscyclopentadienyl-nickel (II) in aprotic solvents, such as for example liquid carbon dioxide (CCM, by reduction with hydrogen. In this case, the solution was heated to above a critical temperature in order to initiate deposition of metal. Patterned films were generated by prior seeding, as described above.
Therefore, the latter process also has the drawback that seeding is required in order to allow patterned deposition of metal. This entails considerable outlay, both in terms of technology and in terms of time and the associated costs.